Previous implementations of content protection use a hard-coded global key and a key exchange in which simple message passing of the new session key is wrapped with the global key. This key exchange involves a single unwrapping of the session key using the previously agreed upon global key, and has been used only for video content protection.
A High Definition Audio (HD-Audio) codec is available that carries out simple key exchange that is proprietary to the specific audio codec, and merely indicates to the application software that the content protected state is ON, assuming that the audio function driver is trusted.
Audio content protection currently is provided using a dedicated content protection session manager implemented in hardware. In order to reduce the complexity of the hardware implementation, a less robust content protection session is typically implemented. For example, a global key generation mechanism is used which exposes the risk of “break once attack all”, where one broken system jeopardizes all systems. Additionally, each audio codec implements its dedicated interface to carry out the key exchange to set up a content protected session and to implement a dedicated decryption engine to decrypt the protected audio data.